Thomas has informed me that the BeOS thread / timer issue has been
covered on the list, so I won't get the discussion started all over
again.

Basically, all I want to know is that if it would be reasonable, until
a proper fix for the timer bugs are introduced, to add a lock around
the timer fire call under BeOS? This would prevent more than one
thread from drawing a document currently being modified, such as when a
keypress event occurs.

The keypress event occurs in the view thread, so when a refresh is
currently taking place a line deletion causes a hard crash when the
refresh thread redraws the deleted line.